The present invention relates to an arrangement for the vibration-isolating or vibration-damped suspension of an electric motor, in particular to a fan motor in a fan housing. A non-rotating motor-supporting element is connected to a support part on at least one side via an integral elastic element. In this case, the supporting element is, in particular, designed as an elongated supporting spindle.
A fan equipped with an arrangement of this type is disclosed in U.S. Pat. No. 2,830,752. In this case, the supporting spindle engages with each of its two ends directly, in a torsion-resistant manner, into a rubber block which, for its part, is mounted in a torsion-resistant manner on a star-like support part. The intention thereby is to prevent, on the one hand, the supporting spindle from becoming distorted and, on the other hand, to dampen vibrations between the supporting spindle and the fan housing.
Similar arrangements are disclosed in DE 41 21 927 A1 and German Patent 1 175 785. Rubber-elastic elements are likewise provided in both cases for mounting the motor.
Many applications have the disadvantage, especially when starting the electric motor, but also in the event of rapid changes in rotational speed, that reaction torques are produced. These torques initially being transmitted to the supporting spindle due to the consistently very rigid connection between the motor or its stator and the supporting element or the supporting spindle. This results in each case in the supporting spindle executing a slight, jerky rotational movement. Using the known rubber elements, it has been demonstrated that these jerky rotational movements of the supporting spindle are disadvantageously transmitted to the particular support part and hence also to the housing. The result is a disturbing development of noise which is audible as a slight "clicking". Especially in applications which make use of motors having a plurality of rotational speed stages, this being the case, for example, in fan motors in exhaust hoods. "Clicking" of this type is audible with every change in rotational speed. If the motor or the fan is used in relatively large-volume appliances having relatively thin side walls, this noise, owing to structure-borne sound transmission, is clearly perceptible and therefore extremely disturbing.
The present invention is based on the object of providing a generic arrangement for the suspension of a motor, with which the development of disturbing noises is effectively reduced.
This is achieved in accordance with the invention in that the elastic element consists of three sections lying axially one behind another. These sections include a support connecting section connected to the support part in a torsion-resistant manner, a motor connecting section connected to the motor supporting element in a torsion-resistant manner, and also of an elastically deformable intermediate section arranged between the two connecting sections.
The concept "in a torsion-resistant manner" is to be understood here, in connection with the invention, as meaning that a relative distortion of the parts connected to one another is eliminated, i.e. there is a safeguard against distortion. To this end, the elastic element is preferably connected to the supporting element and/or to the support part via plug-in connections which are positive in the direction of rotation of the motor and thereby prevent relative distortions. This also makes it possible for the individual parts to be installed in a particularly simple manner simply by plugging them together.
The elastic element according to the invention leads to substantial advantages owing to the special intermediate section. The intermediate section is primarily responsible for the isolating and damping properties of the elastic element, it being advantageously capable of twisting elastically when reaction torques occur. At the same time, the properties with regard to isolating or damping vibrations and reaction torques can advantageously be influenced (set) by the selection of material and/or dimensioning of the length and/or cross section of the intermediate section within a wide range. For instance, the torsional rigidity is increased by enlarging the cross section of the intermediate section, and an axial extension of this section results in a reduction in the torsional rigidity. The jerky rotational movements of the supporting element or the supporting spindle which occur in the event of rapid changes in rotational speed and, in particular, when starting the motor are compensated for and isolated or damped in such a manner, by means of elastic distortions made possible according to the invention, in particular in the region of the intermediate section, that transmission to the support part is virtually ruled out. As a result, disturbing (clicking) noises are reliably avoided.
The following advantages, in particular, can be achieved by the invention:
1) High spring stiffness in the axial and in the radial directions. In the case of use for the suspension of a fan motor in a fan housing, the fan wheel is thereby reliably prevented from grazing against the housing. PA0 2) Low torsional rigidity and, at the same time, a virtually linear spring characteristic. Good vibration isolation also from oscillation torques being superposed on the motor torque. PA0 3) Simple installation preferably without screw connections, i.e. simply by plugging together therefore resulting in a very cost-effective production. PA0 4) Avoiding of vulcanized metal-elastomer connections. PA0 5) Advantageously little influence of, in particular axial, dimensional tolerances of the individual parts of the arrangement according to the invention on the torsional rigidity, and hence on the basic function of the vibration and torsion isolation, since the torsional rigidity of the elastic element is virtually independent of the degree of axial deformation.
Further advantageous refining features of the invention are included in the subclaims and in the description which follows.
The invention will be explained in more detail below with reference to a preferred exemplary embodiment which is illustrated in the attached drawing. In this case, the use in the case of a centrifugal blower is shown by way of example.